Heroin

Heroin is a highly addictive drug and is the most widely abused and most rapidly acting of the opiates. Heroin is processed from morphine, a naturally occurring substance extracted from the seed pod of certain varieties of poppy plants.
Pure heroin, which is a white powder with a bitter taste, is rarely sold on the streets. Most illicit heroin is a powder varying in color from white to dark brown. The differences in color are due to impurities left from the manufacturing process or the presence of additives. Another form of heroin, "black tar" heroin, is primarily available in the western and southwestern U.S. This heroin, which is produced in Mexico, may be sticky like roofing tar or hard like coal, with its color varying from dark brown to black.
Heroin can be injected, smoked, or sniffed/snorted. Injection is the most efficient way to administer low-purity heroin. The availability of high-purity heroin, however, and the fear of infection by sharing needles has made snorting and smoking the drug more common. National Institute on Drug Abuse (NIDA) researchers have confirmed that all forms of heroin administration are addictive.